When shopping for a used airplane it is useful to understand some of the common lingo and acronyms used in aviation classified advertisements.
One of the most important items is the engine time, usually listed as x hours SMOH meaning x hours since major overhaul. Aircraft engine overhauls are expensive. You want an engine that is fairly recently overhauled and no where near TBO. A similar acronym to watch out for is STOH, Since Top Overhaul. This is not a complete overhaul, and is usually done when engine problems occur, or to extend the life of a major overhaul.
SFRM is good to see, if the amount of hours attached is low. This is much like a major overhaul, but better. The manufacturer overhauls the engine at their factory, instead of having a local powerplant tech performing the work. This is not to say that local engine technicians perform substandard work, the manufacturer has technicians who work on only these, and know them better than they know their own kids.
Another important issue is total time. You will see this as TT with the amount of hours of operation of the airframe.
SPOH is another good one to see. It means Since Propeller Overhaul. This is usually only included if it has been done recently. This usually involves making sure there are no major dents and no cracks, the smaller pock marks are smoothed out and the prop is then balanced. Just because it isn’t listed, doesn’t mean the propeller is no good, usually a visual inspection and a ride in the plane to make sure there isn’t excess vibration will be fine.
Airworthiness Directives, AD’s are another item. If not listed, ask the owner if they have been completed. These are memos sent out to the registered owner when the manufacturer or FAA decides that some item on the aircraft needs to be improved/replaced with a better part. They can sometime be very costly, or something simple and cheap, like how the oil filter is secured in place.
The completeness of the engine and propeller logs, as well as airframe logs, are also important factors. These will reflect any major damage history or repairs.
Everything else, for the most part, is up to the buyers discretion. Aircraft without radios are fine, radios can be purchased; the price of the aircraft usually will reflect the amount of equipment onboard. Always verify everything with the seller in person. Having an airframe and powerplant tech perform a thorough inspection is a must as well.
If I have missed anything please /msg me and I will add it.